Electric printing



Jan. 22, 1952 w. HOOPER 2,583,375

ELECTRIC PRINTING Filed Sept. 19, 1945 2 SHEETS--SHEET l zfg/u aiafzfi176 60% we Jan. 22, 1952 w. J. HOOPER 2,583,375

ELECTRIC PRINTING Filed Sept. 19, 1945 2 SHEETS-SHEET 2 2295%@%fizz7z7fdz J67 fiaarce Patented Jan. 22, 1952 ELECTRIC PRINTINGWilliam J. Hooper, Elsah, Ill., assignor, by mesne assignments, toWilliam C. Huebner, New York,

Application September 19, 1945, Serial No. 617,186

This invention relates to electric printing, and more particularly totransfer apparatus and methods wherein transfer is effected byimpression achieved by electrostatic attraction between the sheet andthe liquid carrying member, as the inked roll of a printing press.

One feature of this invention is that it achieves the advantages ofeliminating heavy mechanical impression pressures, so that much lighterweight construction can be used and operation can be at higher speeds,while at the same time actual impression transfer is effected. That is,the moving web of a newspaper press, as one representative example, canbe caused to pass closely adjacent the surface of an inked type cylinderby mechanical means, and then impression pressures suflicient for inktransfer can be effected by electrostatic attraction of the web to theroll, without the use of an impression cylinder or any equivalentthereof.

Moreover, the arrangement is such that the impression transfer efiectedby attraction of the sheet or web to the coated surface is improved byelectrical transfer, the ink source preferably being made negative andthe sheet or web positive.

Other features and advantages of this invention will be apparent fromthe following specification and the drawings, in which:

Figure 1 is an elevational view, partly schematic, of one specificembodiment of my invention utilizing a hot filament as a positive electrode in conjunction with the use of the type cylinder as the negativeelectrode; Figure 2 is a transverse vertical sectional view along theline 2-'2 of Figure 1; Figure 3 is a view similar to Figure 1, butshowing a modified embodiment of my invention; and Figure 4 is anenlarged fragmentary detail view of the printing zone of the apparatusshown in Figure 3.

Printing has for centuries been conventionally effected by mechanicalpressure between an inked member having a design thereon and the sheetto be printed. Very recently, however, it has been found that ink can betransferred from the inked member to the sheet being printed by the useof a field of force, either magnetic or electrostatic, without actualcontact between the inked member and the sheet. Certain arrangementsheretofore proposed for electric printing are shown in such patents asHuebner Patent 1,820,194. of August 25, 1931, and Huebner Patent2,224,391, of December 10, 1940. A full discussion of this type ofprinting will not be set forth here, as reference may be made to theabove-mentioned patents to supplement the present disclosure in 17Claims. (Cl. 101-426) regard to the advantages being sought. It isbelieved suflicient to say that elimination of all need for mechanicalpressure enables very great reduction in the weight and powerrequirements of a large press, a goal toward which the printing industryhas been working for decades.

Electric printing heretofore has been approached on the theory that itinvolved the transfer of the ink across a definite and appreciablespace; i. e., the film of ink on the raised portions of a type cylinder,for example, had to be physically separated from such cylinder andcaused to move across a space of several thousandths of an inch to thesurface of the web or sheet on which printing was to be done. Surfacetension, adherence of the ink to the metal of the type cylinder, and thelike, are strong factors resisting the movement of small droplets orparticles of ink away from the film of ink on the ink source, and highfield strengths and means for facilitating initiation of such movementhave heretofore had to be employed. 1 have found that all of thebenefits of this type of electric printing can be retained, with betterand easier transfer of the ink, by bringing the moving web into goodmechanical contact with the surface of the film of ink on thedesign-bearing cylinder, with pressures between the web and ink film ofthe order of or approaching those used in conventional impressionprinting, but utilizing electrostatic attraction between the web and theink bearing cylinder. While the unit pressures between the web and inkedsurface are high. relatively speaking, the advantages of lighter partsthroughout the press, and elimination of the impression cylinder, arenot lost, since the pressures are created by direct attraction ratherthan by mechanical means. Moreover, the factors effecting transfer inconventional impression printing, such as adherence of the ink to andabsorption of it in the web are assisted by electric action. Theparticles of ink making up the film of ink on the type cylinder, forexample, may have a negative charge, as is commonly the case withconventional inks; and by making the cylinder negative and the webpositive there is a strong electric force of attraction which tends toseparate the ink particles from the surface of the cylinder and causethem to adhere to and remain on the surface of the web.

In view of the newness of electric printing, terminology peculiar tothis art has not as yet come into common use, and the words usedthroughout this specification and claims will be those employed in theconventional printing art. That is, for example, the term "printing isused to describe the operation of delivering ink from the inked memberto the sheet or web being printed, whether this is effected solely bymechanical impression pressure, solely by electric forces, or acombination of the two. That is, the word "printing is used in the broadsense merely to mean transfer from one element to another. It will bealso understood that when one of the rolls or printing members is spokenof as having designs formed on the surface thereof, such designs maycomprise text, pictures, or anything else desired to be printed.Moreover, the designs may be formed on the surface of the printingmember in relief, by intaglio or gravure, or by planographic orlithographic methods. All such methods of forming or preparing aprinting surface are well known in the conventional printing art andneed not be described here, as is also the case in connection withmethods and apparatus for delivering ink to the inked surface in desiredquantities. In reading and interpreting this spec ification and theclaims accompanying it, all terminology borrowed from the conventionalprinting art must be given broad meaning appropriate to this ratherspecial field.

I have made a number of inventions in the field of electric printing,some of the improvements being disclosed but not claimed here beingcovered in other of my copending applications, to which reference may behad, as applications Serial No. 563,473, filed November 15, 1944 nowabandoned; Serial No. 564,574, filed November 22, 1944 now Patent No. 2520,504 dated August 29, 1950; Serial No. 567,605, filed December 11,1944 now abandoned; Serial No. 571,440, filed January 5, 1945 nowabandoned; Serial No. 580,381, filed March 1, 1945 now abandoned; SerialNo. 584,835, filed March 26, 1945 now Patent No. 2, 558,900 dated July3, 1951; Serial No. 590,704, filed April 27, 1945 now Patent No.2,558,901 dated July 3, 1951; and Serial No. 604,618, filed July 12,1945 now abandoned. This application is in particular acontinuation-in-part ofand a disclosure of structures carrying forwardcertain concepts of my applications 580,381, 567,605 and 584,835.

Referring now more particularly to the specific printing apparatus shownin Figures 1 and 2 of the accompanying drawings, a rotating typecylinder l acts as an ink source and as one of the electrode members forcreating an electric field across the printing space. This cylinder ismounted in conventional means, not illustrated, to be rotated about itsaxis I I, and it is electrically grounded throughout. The designs, hereillustrated as in relief on the surface of the cylinder,

. are inked by means illustrated schematically as a conventional inkingsystem comprising the ink trough l2 and the inking rolls ISa-d. Rotationof the cylinder l0 results in continually presenting to the printingpoint or space (directly above the axis of the cylinder, as illustratedhere) a surface area which is at least partly coated with ink in thedesign to be transferred, the raised portions of the type in theparticular case here illustrated carrying ink and the other portions ofthe surface being devoid of ink.

The sheet to be printed is here illustrated as a web of paper H, as aweb of the kind used in newspaper printing. This web moves over a guideroll IS, in contact with the lower ends of the guide members l8 and I1,and over the guide roller l8. This web I4, is of course, driven byconventional web drive means so as to have a lineal speed synchronizedwith the surface speed of the type cylinder l0.

The electric field at the printing point is developed between thecylindrical member ID, as one electrode, and a filament I! as the otherelectrode member. While the filament may be of any suitable material andshape it is here illustrated as a single wire or light rod of some ma-.terial which will not oxidize at high temperatures in air, as platinum.Whether the filament is in one piece or in a plurality of sections, andwhether it comprises straight wire or strip or helically wound wire, itshould in effect lie parallel to the upper surface of the web and spacedslightly therefrom, as to of an inch. It should be heated to a brightred or white heat during use by a low potential source here identifiedas 20. This source may be of any type capable of supplying relativelyhigh currents, as several amperes, at low voltages, as something in theorder of 6-8 volts; and the heating circuit for the filament [8 may becontrolled by a variable resistor, as a resistor here identified as 2 I.

The potential differential between the electrodes l0 and I9 is developedby a variable high potential source here identified as 22. This sourceis adapted to develop a relatively high direct current potential betweenground and its high voltage or hot output terminal, this terminal beingconnected to the electrode filament 19 through a variable resistor 23 ofhigh maximum resistance, as in the order of 100,000 ohms. This highvoltage source may be of a conventional type which can be secured on thecommercial market, as for example those built for highvoltage X-ray tubesupply purposes. Such equipment takes power from an ordinary commercialalternating current source, steps its voltage up to the desired value,and rectifies and filters it to providea high DC voltage. The equipmentpreferably includes manually variable means enabling convenientvariation of the voltage developed, meters by means of which the outputvoltage and current may be determined, and the like. The equipment isnot being further described or illustrated in detail, as it is wellknown and commercially available in forms to meet the voltage andcurrent requirements of apparatus of this type. While the currentrequirements for electric printing are not heavy in the ordinary senseof the word, a very definite current fiow at the instant of printing isdesirable, and, to get a current of at least a few microamperes persquare inch .of printing area at the instant of printing, the highpotential source should be capable of maintaining the desired voltageunder current drains in the neighborhood of or 200 milliamperes.

As has been more fully described and claimed in my earlier applicationsI prefer to have the electrode member away from which the ink travels,during printing or transfer, negative with respect to the otherelectrode member; 1. e., in the press here illustrated, the filament l9would be charged positively with respect to ground, so that thecylindrical member In is the negative electrode in so far as theelectric field is concerned, although it would be at ground potential inso far as the equipment is concerned, so that there would be no dangerto the operator of the press. It may be that negatively charged dropletsor minute ink particles (conventional ink having graphite pigmentparticles suspended in an oil base has negatively charged particles)have their movement away from the inked surface assisted by havingelectrons leave such surface from behind the ink in the direction inwhich it is desired to move the ink; or, as seems more likely, it may bethat a positive ion bombardment effect analogous to that taking place incathode sputtering of metals assists in breaking the ink droplets orparticles away from the ink film and initiating their movement. Whateverthe reason. however, the ink does move readily from the inked surface tothe web when such surface is negative with respect to the web.Accordingly I illustrate the high potential source as having itsnegative terminal grounded and its positive terminal connected throughthe variable resistance 23 to the filament or electrode member 59.

The filament I 9 is shown as mounted in a glass supporting member 24which is vertically adjustable, as by studs 25a and 25b bearing on thevertical portions of the members it and I1. These members in turn arevertically adjustable, extension parts 16a and Ila being carried on theends of the studs 26a and 26b threaded into frame or supporting members21 and 28. The guide members are preferably adjusted vertically untilthey cause the web It to move very closely adjacent the ink film on thesurface of the cylinder [0. preferably in a light contact insufficientto place any mechanical strain upon the parts, the words "closelyadjacent being used to include not only such a light contact but also aslight spacing between the web and cylinder. That is, the mechanicalparts of the press either cause no mechanical pressure at all betweenthe web and the cylinder, or only a light pressure insufficient toeffect satisfactory printing.

The filament I9 is adjusted, by operation of the studs 25a and 25b, soas to cause it to lie slightly above and spaced from the upper surfaceof the web M, as I; of an inch therefrom; and electrostatic forces causethe web to bow" down into rather tight or relatively heavy pressurerelations with the surface of the roll ID at the printing point, butwithout any strain upon the mechanical parts of the press.

It is my theory that the hot filament, raised to a considerable positivepotential with respect to the other electrode member NJ, as 5,000 volts,provides a very rich source of positive ions while substantiallyentirely suppressing negative emission. The positive ions thus createdin the atmosphere immediately above the web and in the upper surface ofthe web cause this upper surface to become relatively highly positivelycharged, with a resultant condenser" action or electrostatic attractionbetween the web and the surface of the cylindrical member I0. Whateverthe explanation of the operation may be, however, I have discovered thatI can secure good printing continuously on moving webs of paper ofsubstantial width by using a hot filament and by making it the positiveelectrode. My experiments to date have indicated that if the electrode[9 is merely a cold metal rod at the same potential differential withrespect to the cylindrical member II] or if it is a hot filament andnegatively rather than positively charged, satisfactory printing willnot result; but that when it is a hot filament, and when it is at apositive potential differential with respect to the cylindrical memberl0, good results are obtained.

Another embodiment of my invention, operating upon the principle ofpositively ionizing the upper surface of the web to effect electrostaticattraction between it and the type cylinder is illustrated in Figures 3and 4, which will now be described. In order to simplify and shorten thedescription of this apparatus, parts thereof which are analogous tothose heretofore described in connection with Figures 1 and 2 will begiven reference numerals 20 higher than those used in the description ofthe first two figures.

In this embodiment of my invention shown in Figures 3 and 4, thetransfer source is again shown as a type roll, being here identified as30, all parts of this cylindrical member being grounded. Inking is againeffected in conventional manner by the inking trough 32 and the inkingrolls 3311-11. A web of paper 34 is shown as passing over the guideroller 35, in contact with the lower surfaces of guide members 33 and31, which may be of plate glass like the members I6 and ll, and over theguide roller 38. The other electrode member adapted to cooperate withthe electrode member 30 is here illustrated as a sheet of light metal,or metal foil 39, mounted between the two parts a and b of glosssupporting means. This supporting means is vertically movable betweenthe center edges of the glass members 36 and 31, as being supported byrotatable studs 45a and 4512. In order to provide for proper adjustmentof the mechanical relationship between the web 30 and the cylinder 30,the guide members 36 and 317 may be supported by rotatable studs 46a and5b engaging frame or supporting members M and 48.

Referring now more particularly to Figure 4, the lower surfaces of theelectrode supporting glass members Ma and Nb may be ground rough andcoated with a radioactive material, these coatings being here identifiedas 49a and Mb. Inasmuch as positive ionization of the air and the uppersurface of the web is what is desired, this material is preferably of atype rich in alpha radiation, as polomum. Radiation from this materialionizes the air in the space immediately above the web 34, in the airchamber defined by the glass members, and the presence of a positivepotential on the electrode member 39 causes the web, and particularlythe upper surface thereof, to become relatively highly positivelycharged. As may be best seen in Figure 3, the potential differentialbetween the electrode members 30 and 39 may be effected by a highpotential source t2 having its negative terminal grounded and itspositive terminal connected through a variable resistor 43 to theelectrode member 39. This form of my invention again causes asubstantial positive ion flow to the upper surface of the web andcharges this to a relatively high positive potential differential withrespect to the type cylinder 30, causing the forces of electrostaticattraction to bring the web into good printing engagement with thecoated surface of the cylinder 30, the mechanical pressures beingappreciable and the transfer action of these pressures being assisted byelectric forces on the ink.

While I have shown and described certain embodiments of my invention, itis to be understood that it is capable of many modifications. Changes,therefore, in the construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims.

I claim:

1. Transfer apparatus of the character described, including: a source ofliquid to be transferred; means for supporting sheet material adjacentsaid source; means for developing a high- 7 affecting ionization in saidspace on the positive field gradient side of said sheet material.

2. Transfer apparatus of the character de scribed, including: a sourceof liquid to be transferred; means for supporting sheet materialadjacent said source; means for developing a high potential electricalfield across a space including said source and the sheet materialadjacent; said source and means independent of said field for providingionization in said space.

3. Transfer apparatus of the character described, including: a source ofliquid to be transferred; means for supporting sheet material adjacentsaid source; means for developing a high potential electrical fieldacross a space including said source and sheet material; and ionizingmeans comprising a hot filament in said space.

4. Transfer apparatus of the character described, including: a source ofliquid to be transierred; means for supporting sheet material adjacentsaid source: means for developing a potential differential across aspace including said source and the sheet material adjacent said sourceand ionizing means comprising a hot filament as the positive electrodeof the means for developing a potential differential.

5. Printing apparatus of the character described, including: a rotatingcylindrical member having at least a portion of the surface thereof.coated with ink to be transferred; means for moving a web of sheetmaterial and causing it to pass closely adjacent said coated surface;means for developing an electrostatic field across a space includingsaid ink and the web of sheet material adjacent said coated surface, thelast mentioned means comprising said cylindrical member as a negativeelectrode and a positive electrode member spaced therefrom; and ionizinmeans comprising a hot filament on the opposite side of said web fromthe said cylindrical member.

6. Printing apparatus of the character described, including: a rotatingcylindrical member having at least a portion of the surface thereofcoated with ink to be transferred; means for moving a web of sheetmaterial and causing it to pass closely adjacent said coated surface;and means for developing a potential differential across a spaceincluding said ink and the web of sheet material closely adjacent saidcoated surface, the last-mentioned comprising said cylindrical member asa negative electrode and a hot filament spaced therefrom as a positiveelectrode.

7. Printing apparatus of the character described, including: a rotatingcylindrical member having at least a portion of the surface thereofcoated with ink to be transferred; means for moving a web of sheetmaterial and causing it to pass closely adjacent said coated surface;means for developing a potential differential across a space includingsaid ink and the web of sheet material closely adjacent said coatedsurface, the lastmentioned means comprising said cylindrical member as anegative electrode and another electrode member spaced therefrom; andradio-active material on the positive field gradient side of said web.

8. Printing apparatus of the character described, including: a rotatingcylindrical member having at least a portion of the surface thereofcoated with ink to be transferred; means for moving a web of sheetmaterial and causing it to pass closely adjacent said coated surface;means for developing a potential differential across a space includingsaid ink and the web of sheet material closely adjacent said coatedsurface, the lastmentioned means comprising said cylindrical member as anegative electrode and another electrode member spaced therefrom; andradio-active material on the positive field gradient side of said web,this material being closely adjacent the positive electrode.

9. Printing apparatus of the character described, including: a rotatingcylindrical member having at least a portion of the surface thereofcoated with ink to be transferred; means for mov ing a web of sheetmaterial and causing it to pass closely adjacent said coated surface;means for developing a potential differential across a space includingsaid ink and the web of sheet material closely adjacent said coatedsurface, the last mentioned means comprising said cylindrical member asa negative electrode and another electrode member spaced therefrom; andradio-active material on the positive field gradient side of said web,this material being of a character particularly effective in creatingpositive ions in the air in said space.

10. The method of transferring liquid from a source thereof to a sheet,comprising bringing the sheet adjacent the source by mechanical meansand bringing the sheet into liquid transferring contact with the liquidsource by the pressure created by electrostatic attraction between thesheet and said liquid source.

11. The method of transferring liquid to a web by use of a rotatincylindrical member, comprising coating at least a portion of the surfaceof said member with said liquid, causing said web to pass closelyadjacent said coated surface by mechanical means, and bringing the webinto liquid transferring contact with the coated surface by the pressurecreated by electrostatic attraction between the said web and thecylinder member.

12. The method of transferrin liquid to a web by use of a rotatingcylindrical member, comprising coating at least a portion of the surfaceof said member with said liquid. causing said web to pass closelyadjacent said coated surface by mechanical means. and impartingelectrical charges to said web and cylindrical member, the charge onsaid web being of opposite polarity with respect to said cylindricalmember to bring the web into liquid transferring contact with the coatedsurface by the pressure created by electrostatic attractiontherebetween.

13. The method of transferring liquid to a web by use of a rotatingcylindrical member, comprising coating at least a portion of the surfaceof said member with said liquid, causing said web to pass closelyadjacent said coated surface by mechanical means, and giving said web ahigh density electric charge of opposite polarity with respect to saidcylindrical member to bring the web into pressure contact with thecoated surface by electrostatic attraction therebetween.

14. The method of transferring liquid to a web by use of a rotatingcylindrical member, comprising coating at least a portion of the surfaceof said member with said liquid, causing said web to pass closelyadjacent said coated surface by mechanical means, giving said web anelectric charge by supplying positive ions to the web, and rendering thesaid cylindrical member negative relative to said web to bring it intopressure contact with the coated surface by electrostatic attraction.

15. Transfer apparatus of the character described, including: a rotatingcylindrical member having at least a portion of the surface thereofassasvs coated with liquid to be transferred; mechanical means formoving a web of sheet material and causing it to pass closely adjacentsaid coated surface, this means leavin the web tree to contact saidsurface; and means for bring the sheet into transferring contact withthe surface of said member by electrostatic attraction, this meansincluding a hot filament.

16. Transfer apparatus of the character described, including: a sourceof liquid to be transferred; means for supporting a sheet adjacent saidsource; means for developing a potential differential across a spaceincluding said source and a sheet supported adjacent said source andmeans independent of said potential diiierential producing means forionizing air in said space.

1'7. Transfer apparatus of the character described comprising a memberadapted to have at least a portion of the surface thereof provided witha fluid to be transferred, an electrode spaced 10 from said member,means for supportin sheet material adiacent said member intermediate thelatter and said electrode, a source of high potential electrical energyconnected to provide an electrostatic field between said electrode andsaid member, and means independent of said source of high potentialsupplying ions to the space adjacent said electrode. 4

WILLIAM J. HOOPER.

REFERENCES CITED The following references are of record in the flle 01'this patent:

UNITED STATEB PATENTS

